The Court of Appeal in its judgement did not doubt that this appeal would be allowed. Lord Taylor accepted that “Even if a number of bands correspond exactly, any discrepancy between the profiles, unless satisfactory explained, will show a mis-match and will exclude the suspect from complicity.” Consequently, a retrial was ordered. Secondly, the phenomenon of degradation may be responsible for inconclusive results. DNA is an organic compound and therefore liable to recycling into the environment. According to Inman and Rudin (1997, p.11) degradation occurs when a DNA molecule breaks into smaller fragments and as a result the bands of DNA are less than the minimum for the needs of the profiling process. Factors that can cause degradation of DNA include time, temperature, humidity, light and the presence of insects.
As a fact, degradation can have effect on the ability to obtain a useful result from DNA typing. Degraded samples may be responsible for another phenomenon known as “band-shifting.”25 Accordingly, degraded DNA may not run in the gel at the same speed as it would in ideal DNA samples. This makes the bands shifting up and down in relation to each other. Therefore, even if both profiles have come from the same perpetrator, the band will have different placements on the autobiographies. Nevertheless, even if band-shifting occurs the scientists may still be able to declare a match as soon as the bands have not had a significant shift.
As it has been presented, the procedure is quite dangerous as there is no critical approach by both lawyers and scientists. As hall (1990) criticises, DNA evidence becomes a black box in which scientific evidence are put from the one side and the verdict is being produced at the other26. The reason for such a similitude is that simply both lawyers and jurors may not be able to keep up with the scientific analysis of DNA evidence. The Jurors will have to prepare their verdict by considering the results of a quite complex process.
Following the Dean, case new methods have been invented to combat the many criticisms of the RFLP process. The new methods are based on the STR27 technique. This pioneering process looks only at specific areas of the DNA that are known to vary widely between people, and therefore are extremely useful for the purposes of criminal investigation. STR, in antithesis with RFLP, is immune to problems occurring from discrepancies in the profiles or from degradation and therefore it is a more stable and reliable.
Nevertheless, there might be the case where the scientists declare a match between a DNA profile from the crime stain and from a suspect who is not the true source of the sample. DNA evidence is not unique for each person and therefore it is possible for two people chosen randomly to have the same DNA profile. Thus, there is a probability that a match can be declared due to random match probability. This probability is calculated by population geneticists from existing DNA databases28.
Furthermore, it has been argued that examiner bias may lead the scientist who compares the profiles to declare a match. Moreover, it might be a person related to the offender. It has been argued that brothers have quite similar DNA profiles and therefore if a scientist does not pay the necessary attention he might declare a match negligently. In a conversation in the House of Commons, Dr. Werrett reported that he had faced instances were a suspect alleged the brothers defence and additionally he said that the suspect had six brothers who were not willing to give a sample.29
Although, as discussed above, the DNA technology has been developed and such errors are not likely to occur frequently, in principle there is still a possibility for such errors as human interpretation is still required.30
Of course, there might be the case where an innocent defendant is the true source of a match report is the true source of a match. A study carried out carried out by J. Tobasco31 showed that it is very possible for DNA to be transferred following actions as simple as a kiss. In his study the participants required to kiss each other for a period of 5 seconds and then smoke a cigarette. Analysis of the cigarette butts showed that 67% had of them had DNA from the person they were kissing. This study purports that it is possible that an innocent girlfriend of murdered victim would be incriminated if the victim has kissed her and afterwards has smoked a cigarette before his murder.
Estimation of Match Probability
Following the declaration of a match, the scientist must estimate the random match probability or the likelihood ratio which reflects the probability that the DNA profile of a random chosen person matches the crime stain. This depends on the number of the bands that match between two profiles and the genes frequency which appears in the relevant population of such band matching, as it was explained in R v Gordon32.
Nonetheless, the statistical evaluation of a match has been hazardous area of DNA Profiling, up to date. Swenson and Coleman (1995) regard it “as the most contentious debate in respect of DNA evidence”. One of the reasons of criticism is that this process is quite complex. The statistical interpretation requires the scientists to conclude into a discriminative result, after comparing the DNA profile with the other samples from the available database. And whilst population studies have shown that there exist significant differences in the frequency of genes between ethnic groups, other studies have shown that there are a lot of similarities in all populations.33 However, it has been proved that the differences in the frequency of genes are much more than the similarities34.
Currently in England there are four databases available to the Forensic Science Service with separate sub-sets for the Afro-Caribbean, Asian and Caucasian populations35. It has been argued that the systems used to calculate such differences may be biased in favour of the suspect producing unreliable results, where the suspect belongs to a subpopulation. For instance if the defendant is Sierra-Leonean, the afro-Caribbean database might not have enough DNA samples of that ethnic origin to produce an accurate estimation.
The reliability of the DNA database concerned the court In R v Musa-Gbengba,36 where a new jury direction was given in respect to the statistical significance of the Crown DNA evidence. Although, the defendant’s origin was Sierra Leonean, the prosecution used an Afro-Caribbean database to estimate the match probability. The defence counsel argued that the match probability produced by the general Afro-Caribbean database was inaccurate and therefore its weight should be reduced.
This argument was empowered by evidence from the cross-examination of the prosecutions’ expert, who testified that in the chosen database there was no representation of the defendant’s origin. Thus, the Judge gave a direction to the Jury to change the match probability if it accepted that the defence’s submission was correct. Following the Judgement in R v Musa-Gbengba37, in R. v. Alan James Doheny38, the court ruled that the Forensic Science Service should make available to the defence expert, the databases that were used to estimate the match probability.
PART B “Retention of DNA evidence and the Future” The police power to retain DNA fingerprint samples has been a matter of concern for the English courts of justice, particularly for challenging the admissibility of DNA evidence. Since 1984, the police powers to obtain samples from persons involved in criminal investigations have been increasing. However, such powers of the police have been heavily opposed by civil liberties supporters. There have also been cases39 in which the legislative bodies where claimed to be in breach of the right to privacy and the right non-discrimination. Nevertheless, since the establishment of the National DNA database in 1994, the English government tends to support the development of the database.
2.1 The Development of Law The Police and Criminal Evidence Act 1984 was the first body which enabled the police to take samples from a suspect who was connected with the investigation of an offence. The PACE separated such evidential samples into two categories; the intimate samples and the non-intimate samples.
Following the Pace, the Criminal Justice and Public Order Act 1994 made significant changes to the PACE in respect with the conditions that a sample maybe taken from suspects in order to produce a DNA profile for the purposes of criminal investigation. Accordingly, the police was given the power to take an intimate sample from a detained person as soon as an officer with the minimum rank of a superintendent had reasonable grounds for suspecting such person for a recordable offence. Recordable offences include all imprisonable offences. It has to be reminded, that ALL offences are imprisonable, with the exception of “obstruction of the Highway” and “breach of the peace”. So practically, the police had the power to take samples from any detained suspect person.